Tiltable search antenna pedestal



TILTABLE SEARCH ANTENNA PEDESTAL 4 Sheets-Sheet 1 Filed Nov. 23, 1951 FIG.

CHARLES W. CAIRNES INVENTOR.

ATTURIWYS Oct. 4, 1955 c. w. CAIRNES 2,719,921

- TILTABLE SEARCH ANTENNA PEDESTAL Filed Nov. 23, 1951 '4 Sheets-Sheet 2 CHARLES W. CAIRNES INVENTOR.

AT T ORNE Y5 Oct. 4, 1955 c, w, c N 2,719,921

TILTABLE SEARCH ANTENNA PEDESTAL Filed Nov. 23, 1951 4 Sheets-Sheet 4 FIG 4 CHARLES W CAIRNES INVENTOR.

ATTORNEYS United States Patent ()fiice 2,719,921 Patented Oct. 4, 1955 TILTABLE SEARCH ANTENNA PEDESTAL Charles W. Cairnes, Towson, Md., assignor to Bendix Aviation Corporation, Towson, Md., a corporation of Delaware Application November 23, 1951, Serial No. 257,811

7 Claims. (Cl. 25033.65)

This invention relates to radar search antenna arrangements and more particularly to an improved search antenna mount adapted to be continuously rotated in azimuth and selectively tilted during rotation to any desired angle of elevation.

Prior art devices to this end have generally provided a manual adjustment of the tilt angle, in which case the azimuth rotation was required to be interrupted while the adjustment was made. Alternatively, an electric motor has been employed for driving tilting means which was mounted for rotation with the antenna pedestal. Such a motor was required to be energized from stationary controls by means of slip rings and provided no means for manual control in the event of electrical failures in the motor-control circuits.

The construction of rotating antenna pedestals of this type presents certain problems which are peculiar thereto with respect to size, reliability, and constructional features. Search antennas are usually mounted on elevated platforms or on the roof of mobile units which house a large quantity of related equipment, both situations requiring compact reliable pedestal assemblies which may be readily serviced and which will withstand exposure to the weather. Further design limitations are due to the requirement of some manner of transferring radio frequency energy between the stationary and rotating por tions. The rotating portions of systems of this type are generally exposed to the weather with the consequent aggravated problems of lubrication of moving parts and providing sufficient margins of strength in the bearing designs to withstand wind loading of the antenna structure.

It is an object of the present invention to provide a new and improved tiltable search antenna pedestal.

A further object is to provide a tiltable antenna pedestal which may be tilted during rotation by manual or power means.

Another object is to provide a pedestal assembly which may be easily serviced from the under side thereof and has a minimum projection above its mounting surface.

Another object is to provide a compact reliable pedestal assembly which is capable of supporting a large antenna structure having large wind loading and providing for continuous rotation thereof with adjustable tilt control of the rotating base.

These and other objects of the present invention are realized in the preferred embodiment thereof by the provision of an antenna base plate rotatably mounted by a ring thrust bearing to a stationary base. A jack screw is rotatably mounted on the antenna base plate and its rotation is under the control of two gear trains operated from two stationary ring gears. The gear trains operate differentially in such a manner that the jack screw remains normally stationary with respect to the rotating base plate. When relative motion is imparted to the ring gears the jack screw is turned thereby moving a jack nut along the jack screw and tilting the antenna reflector.

The aforementioned and other objects and the operation of the invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings wherein:

Fig. 1 is a perspective view of the antenna-reflector mounted on the pedestal base assembly;

Fig. 2 is a plan view of the pedestal base with the antenna-reflector removed;

Fig. 3 is a sectional view along the line 33 of Fig. 2;

Fig. 4 is a pictorial view, partially cut away, of the assembly; and

Fig.5 is a fragmentary sectional view along the lines 5-5 of Fig. 3.

Referring now to Fig. 1, there is shown a horn assembly 10 and a reflector surface 11 secured to a supporting frame 12 which is hinge mounted to a base plate 13 by mating hinge members 14. The antenna-reflector assembly is secured by means of a mounting flange 9 to a jack nut assembly 15 and tilts about the axis of the hinges 14 upon vertical motion of the jack nut 15. The an tenna and base plate assembly is removably mounted on a stationary section 16 of the mechanism which is mounted to a support surface 17, all of which will more fully appear hereinafter. The electrical input to the horn assembly is accomplished by means of a section of flexible waveguide 18 joining the horn input and the output ofa waveguide rotary joint. This rotary joint is the subject of the application of William G. Alexander, Serial No. 261,259, filed December 12, 1951, and assigned to the same assignee as the instant invention.

In Fig. 2 the rotatable base plate 13 is shown having hinge members 14 and the jack nut 15. The base plate 13 is secured to a top plate 19 which rests on the inside race of a ring bearing as will be hereinafter described.

The details of the rotating top plate 19 and planetary gearing assembly will now be described with reference to Figs. 3 and 4 jointly, certain features being displayed with greater clarity in one view than the other. The top plate 19 is secured to the inside races of a pair of ring thrust bearings 21. The outside races thereof are secured to a stationary portion 22 of the pedestal. The stationary portion 22 has a flange 20, whereby it may be secured to the support surface 17.

The top plate 19 has a vertical rim portion 23 which supports an inside ring gear 24. The top plate 19 has bolted thereto a U-bracket 25 and rotatably supported thereon is an epicyclic gear cluster to be more fully described hereinafter. The base plate 13 has mounted thereon a jack screw bearing housing 26 which is aligned with the axis of the epicyclic cluster and the assembly secured to the top plate 19. Axial alignment is secured by the circular register means 27. The housing 26 contains a pair of thrust bearings 28, rotatably supporting a socket member 29. The socket member 29 is adapted to receive a mating ball member 30 which is integrally formed on the end of the jack screw 31. The jack screw 31 supports the jack nut assembly 15 which includes the jack nut proper 32 and the weather seal and oil sump cup 33. Pivotally connected to the jack nut proper 32 is an adapter collar 34. The collar 34 contains threaded portions 35 for receiving and securing the mounting flange 9 on the base of the antenna reflector assembly to the jack nut 15. Relative adjustment of the antenna beam and the position of the collar 34 may be initially made by means of a suitable number of shim pieces 8. The adapter collar 34 has an opening therein sufficient to permit the jack screw to tilt with respect to the antenna and secures, by means of a pivot 36, the jack nut from rotation with the jack screw. An impregnated cloth bellows 37 is secured to the base of the collar 34 and to the top of the housing 26 to effect a flexible weather seal. When the jack screw assembly mounted in housing 26 is in place over the epicyclic cluster secured by bracket 25,

the socket 29 has spring actuated pins 38 which extend into mating recesses in the output gear 39 of the cluster thereby to drive the socket member 29 in rotation with the gear 39. The motion of the socket 29 is imparted to the ball of the jack screw 31 by means of a slot and pin arrangement to be more fully described hereinafter.

The stationary base portion 22 has mounted on it by means of ball bearing 41 the stationary portion of a waveguide rotary joint 42. The stationary member 22 has fixedly mounted thereon a ring gear 43 and rotatably mounted thereon a ring gear 44. The ring gear 44 is maintained normally stationary with respect to the frame member 22 by engagement with a geared shaft 45 of a motor, having magnetic brake means associated therewith for maintaining the shaft 45 and gear 44 in engagement therewith in a stationary position in the absence of rotation of the motor shaft. An extension of the shaft 45 forms a crank shaft 50 which may be turned by a suitable hand crank for manual adjustment of the antenna tilt. Also mounted on the stationary member 22 is a motor driven geared shaft 46 in engagement with the ring gear 24 on the rotating base plate 19 for imparting rotary motion to the rotatable portion of the pedestal assembly upon energization of the motor to drive the shaft 46.

The epicyclic cluster which is mounted to the rotating plate 19 by the bracket 25 has two input gears 47 and 48 respectively engaging the ring gears 43 and 44. The gear 48 is integral with a gear 49 which drives planetary gears 51 which are rotatably mounted on shafts fixed in the body of gear 47. The output gear 39 has inside teeth meshing with the planetary gears 51. The gear ratios between gears 43, 47, 51 and 39 is equal to that from gears 44, 48, 49, 51 and 39, and through the differential action thereof maintains the output gear 39 stationary with respect to rotation about its own axis as the pedestal assembly rotates and the respective input gears 47, 48 of the cluster ride in the stationary ring gears 43 and 44. When motion is imparted to gear 44, by means of rotation of the motor shaft 45, the change in relative motion between the input gears of the cluster is such that the differential action thereof drives the output gear 39, thereby turning the jack screw through the pin coupling hereinbefore described. In this manner, the height of the jack nut 32 and the collar 34 mounted thereon is adjusted by rotation of the ring gear 44 for either rotating or stationary conditions of the top plate 19. Hence the tilt angle of the antenna, hinge secured to the base plate 13 and the collar 34, may be readily adjusted by means of the control motor 45 or manually by crank shaft 50, while the entire search antenna-reflector and pedestal assembly is in continuous rotation.

Fig. shows the details of the drive coupling between the socket 29 and the ball 30 for rotating the jack screw 31. The ball 30 has two vertical diametrical opposite slots 53 therein. The socket member 29 carries two pins 54 which extend into the socket opening and into the slots 53. Upon rotation of the socket block 29 the pins 54 bear against the walls of slots 53 and rotate the ball 30 and screw 31. The ball and socket universal action of the assembly is not impaired by the pins 54 due to the clearance 55 between the ends of the pins 54 and the bottom of the slots 53. The dimensions of the clearance 55 are determined by the maximum tilt required of the screw 31 in a given application.

The pedestal of the present invention is well adapted to be constructed with the waveguide rotary joint 42 incorporated therein along the axis of rotation of the top plate 19. The waveguide rotary joint itself forms no part of the present invention and is disclosed and claimed in the aforementioned copending application.

Many modifications will be apparent to those skilled in the art in the light of the above teachings and are to be understood as being within the scope of the present invention.

What is claimed is:

l. A rotating pedestal for a search antenna comprising, a stationary base, a plate rotatably mounted on said base, a differential planetary gearing assembly carried by said plate and having its axis parallel and offset with respect to the axis of rotation of said plate, means for rotating said plate, a pair of normally stationary ring gears concentric with said axis of rotation and drivably engaging the differential input gears of said assembly in ratio to maintain the output gear thereof stationary on said plate, a jack screw mounted for rotation on said plate and axially aligned with the axis of said assembly, a universal joint drivably connecting said jack screw with the differential output gear of said assembly, a jack nut for said screw, a collar member pivotally mounted to said nut, a hinge member on said plate remote from said jack screw, and means operable at will for imparting relative rotation to said ring gears, whereby an antenna having a rigid base fixedly supported on said collar and hinge supported at said hinge member will be tilted about the hinge axis upon relative motion of said ring gears.

2. A rotating pedestal for a search antenna comprising, a stationary base, a plate rotatably mounted on said base, a differential planetary gearing assembly carried by said plate and having its axis parallel and offset with respect to the axis of rotation of said plate, means for rotating said plate, a pair of normally stationary ring gears concentric with said axis of rotation and drivably engaging the differential input gears of said assembly in ratio to maintain the output gear thereof stationary on said plate, a jack screw having a ball on the end thereof and axially aligned with the axis of said assembly, said ball having a pair of slots therein parallel to said axis, a socket member for said ball having pivot pins engaging said slots and rotatably mounted on said plate, means drivably connecting said socket member to the differential output gear of said assembly, a nut for said screw, a yoke member pivotally mounted to said nut, a hinge member on said plate remote from said jack screw, and means operable at will for imparting relative rotation to said ring gears, whereby an antenna having a rigid base fixedly supported on said yoke and hinge supported at said hinge member will be tilted about the hinge axis upon relative motion of said ring gears.

3. A rotating pedestal for a search antenna comprising an annular stationary base, a pair of ring thrust bearings secured to said base in opposite thrust bearing relation, a first ring gear fixedly secured to said base, a second ring gear rotatably secured to said base, means for selectively controlling the rotation of said second gear, a second annular base secured to the rotatable portions of said bearings and rotatable therewith, the openings in said annular bases being in substantial alignment, a ring gear fixedly secured to said second base, means drivingly engaging said last named ring gear, for rotating said second base, a differential gear cluster mounted on said second base with the differential input gears thereof in planetary engagement with respective ones of said first and second ring gears, the drive ratios of said differential inputs from said ring gears being such that the differential output is stationary with respect to said second base for one rotational condition of said second gear, means adjustable in elevation on said second base plate, means for driving said adjustable means for elevational variation from said differential output, hinge means on said second base plate remote from said adjustable means for pivotally supporting said antenna, and means drivably connecting said antenna to said adjustable means for tilting said antenna around the axis of said hinge means.

4. A rotating pedestal for a search antenna comprising a stationary base member having an opening therein, a rotatable base mounted for rotation on said stationary base and having an opening therein, said openings being in substantial alignment, a pair of ring gears on said stationary base and relatively rotatable around said opening, a differential gear cluster mounted on said rotatable base with the differential input gears thereof in planetaryengagement with respective ones of said ring gears, the drive ratios of said differential inputs from said ring gears being such that the differential output member is stationary with respect to said rotating base in the absence of relative rotational motion between said ring gears, means for tiltably mounting said antenna on said rotating base, means driven by the motion of said differential output member for tilting said antenna, and means for selectively imparting relative rotation to said ring gears.

5. A rotating pedestal for a search antenna comprising a stationary base member having an opening therein, a rotatable base mounted for rotation on said stationary base and having an opening therein, said openings being in substantial alignment, differential gearing including three elements relatively movable and mounted on said rotatable base, two independent planetary gear trains each having their sun gears around said opening in said stationary base and concentric with the center of rotation of said rotatable base and their planet gears independently drivably connected to two elements of said differential, means for tiltably mounting said antenna on said rotating base, means drivably connected to the third element of said ditferential for tilting said antenna, and means for selectively imparting relative motion to said sun gears to drive said third element.

6. A rotating pedestal for a search antenna comprising a stationary base member having an opening therein, a rotatable base mounted for rotation on said stationary base and having an opening therein, said openings being in substantial alignment, differential gearing including three elements relatively movable and mounted on said rotatable base, two independent planetary gear trains each having their sun gears around said opening in said stationary base and concentric with the center of rotation of said rotatable base and their planet gears independently drivably connected to two elements of said differential, means for tiltably mounting said antenna on said rotating base, an antenna base member, a threaded shaft mounted for rotation on said rotating base, a universal joint drivably connecting said shaft to the third element of said differential, a nut threadedly engaging said shaft, a yoke pivotally connected to said nut, hinge means remote from said shaft for tiltably supporting said antenna base on said rotatable base, means for fixedly supporting said antenna base on said yoke, and means for selectively imparting relative motion to said sun gears to drive said third element.

7. A pedestal for supporting a rotating element comprising a stationary base member, a rotatable base member mounted for rotation on said stationary base, a pair of ring gears on said stationary base member and relatively rotatable thereabout, a differential gear cluster mounted on said rotatable base with the differential input gears thereof in planetary engagement with respective ones of said ring gears, the drive ratios of said differential inputs from said ring gears being such that the differential output member is stationary with respect to said rotating base in the absence of relative rotational motion between said ring gears, means for tiltably mounting said element on said rotating base, means on said rotatable base driven by the differential output member for tilting said element, and means for selectively imparting relative rotation to said ring gears.

References Cited in the file of this patent UNITED STATES PATENTS 

